THE EFFECT OF DOSE LEVEL OF INTRAVAGINAL PROGESTAGEN ON SPERM TRANSPORT, FERTILIZATION AND LAMBING IN THE CYCLIC MERINO EWE

Abstract

Summary. The numbers of spermatozoa recovered from the Fallopian tubes 24 hr after insemination, fertilization rate and lambing were measured in one group of 120 normal cyclic ewes and in three groups of 120 animals which had been synchronized with intravaginal sponges impregnated with 10, 30 or 90 mg Cronolone (Searle). Half of each group received 500 i.u. pmsg. Results were as follows: pmsg had no apparent effect on any one of the three parameters. Increasing dose of progestagen significantly increased the incidence of oestrus and was associated with an increasing ovarian response to pmsg. There was no evidence that embryonic mortality was greater in progestagen-treated than in untreated ewes. Considering all parameters of fertility, ewes treated with intravaginal sponges containing 10 mg Cronolone yielded the fewest spermatozoa, the lowest number and percentage of fertilized eggs and the lowest percentage of lambing ewes.